In a known manner, a logic module is a device that performs a logic function and usually comprises several inputs and one or several outputs, each output being obtained by performing one or several binary logic operations on the inputs. A distinction can be made between “combinational” logic functions on which boolean calculations are based, resulting from a combinational analysis of variations of input magnitudes only, and “sequential” logic functions or toggles resulting from the association of several “combinational” logic functions for which there must be a “clock” that sets the rhythm; output values depend not only on input values, but also on the time at which they are measured (before or after clock synchronisation).
It should be noted that when an input data is modified, the output reacts immediately, except for the propagation time. This specific feature has disadvantages. The output data are lost when a power supply failure occurs. This power supply failure may be accidental, but it may also be deliberate so as to reduce the global consumption of the circuit.